纤维增强树脂基复合材料的搅拌摩擦焊研究

利用搅拌摩擦焊实现了纤维增强树脂基复合材料的焊接,获得了焊接接头力学性能并分析了接头形成和断裂机制。结果表明,由于搅拌摩擦焊过程中搅拌针的摩擦剪切及对塑化材料的挤压作用,使树脂基体发生塑化并带动碳纤维迁移形成焊接接头,在搅拌头旋转速度950 r/min,焊接速度38 mm/min时,接头拉伸强度可以达到52.43 MPa,接近母材强度的51%,焊接接头的断裂机制主要为基体剪切断裂和纤维-基体界面脱粘。     

6061铝合金搅拌摩擦焊焊缝微弧氧化涂层的耐蚀性

对6061铝合金搅拌摩擦焊(FSW)焊缝进行微弧氧化(MAO)处理来提高其耐蚀性能。采用扫描电子显微镜(SEM)和X射线能谱仪(EDS)分析了FSW焊核区与母材区的表面和截面形貌及其组成,通过极化曲线和电化学阻抗谱(EIS)研究了焊核区、母材区微弧氧化前后的耐蚀性能,并通过盐水浸泡实验进一步验证了其耐蚀性。微弧氧化涂层能够显著提高搅拌摩擦焊接头的耐蚀性能,且焊核区微弧氧化涂层的耐蚀性比母材区微弧氧化涂层更好。     

大直径铝合金压力容器椭圆形拼焊封头研究

分析了在两个不同标准下设计的直径3350 mm的铝合金椭圆形封头的差异。采用母材与焊缝分别计算的方法,设计了适用于工程实际的等匹配椭圆形拼焊封头。在0.56MPa承载条件下,母材设计厚度为4.98 mm,焊接区设计厚度为8.3 mm,单侧减薄过渡,焊缝加厚区的宽度不小于40 mm。用单面两道的焊接方式拼焊封头时,焊缝断口位于热影响区,封头焊接区安全系数达到2.77。     

Q345R双面埋弧焊接头组织分析

采用双面埋弧焊方法焊接了20mm厚的Q345R钢,分析了接头焊缝区及热影响区的组织并进行了显微硬度测试。组织分析表明,焊接接头焊缝区为柱状晶,组织为先共析铁素体、少量针状铁素体和珠光体;热影响区靠近焊缝处为等轴晶,组织为先共析铁素体+少量珠光体,离焊缝较远处为铁素体与珠光体相间的带状组织,珠光体有一定程度的减少。显微硬度分布表明,接头热影响区硬度最高,焊缝硬度高于母材硬度。     

不同焊接方法下超细晶粒钢焊接接头研究

用手工电弧焊和CO_2气体保护焊焊接超细晶粒钢WCX355,研究并对比了两种焊接方法下超细晶粒钢焊接接头。结果表明:由于采用的是2.5mm焊条、低的焊接电流和快的焊接速度,超细晶粒钢手工电弧焊焊缝区在电流较小时多呈等轴晶,随着电流的增大树枝状晶增多。而超细晶粒钢CO_2气体保护焊由于采用的电流较大,焊缝区均为树枝状晶。过热区的组织随焊接电流增大而增大,CO_2气体保护焊的过热区比手工电弧焊的过热区组织形貌分布更均匀。两种焊接方法下正火区均为比母材细小的铁素体和珠光体。两种焊接方法下,超细晶粒钢的焊接接头硬度均高于母材,未出现软化现象。     

固溶处理对Q235/316L异种钢焊接接头显微组织及力学性能的影响

采用手工电弧焊对Q235/316L异种钢进行焊接,焊后使用电阻炉对焊接接头进行不同温度的固溶处理,然后对焊接接头进行显微组织分析和力学性能研究。结果表明:固溶处理后,焊缝区组织比较均匀,力学性能得到改善;焊接接头的拉伸断裂均发生在Q235母材区,抗拉强度最大值为568MPa;焊缝区的韧性随着固溶温度的升高而增加,焊缝区的硬度有所降低,但高于Q235母材和316L母材的硬度。     

保温时间对低体积分数SiCp/A356复合材料真空钎焊影响

在真空度为10-3 Pa、加热速率为20 ℃/min、加热温度为565℃的条件下,使用Al-5 Si-28Cu-Zn-Ti钎料,采用不同保温时间分别对体积分数20％的SiCP/A356复合材料进行真空钎焊,测定了钎焊接头的抗剪切强度以及接头显微硬度,分析了不同保温时间对钎焊接头性能的影响.结果表明,接头抗剪强度和焊缝硬度均随保温时间的延长先增加后减小.当保温时间25 min时,钎焊接头抗剪强度最大,为28.35 MPa,此时,焊缝硬度最高,为127.2HV.对比不同保温时间下钎焊接头综合性能,25 min保温时间最好.     

LD10铝合金搅拌摩擦焊技术研究

本文对LD10铝合金摩擦塞焊技术进行了研究,采用扫描电镜,显微硬度等手段分析摩擦焊焊缝组织变化规律,采用LD10铝合金平板进行摩擦焊实验研究,取摩擦塞焊接头塞棒与板材配合角度,二级焊接速度等参数进行摩擦塞焊接正交实验。LD10铝合金拉锻式摩擦塞焊缺陷有塞棒中部底部结合面未焊合等,体粗减少缺陷的措施。     

Ni-P/nano-Al_2O_3复合镀层的制备及性能

以汽车模具配件—导柱常用的20Cr钢为基材,在其表面制备Ni-P/nano-Al_2O_3复合镀层及普通Ni-P镀层。对Ni-P/nano-Al_2O_3复合镀层的微观形貌、晶相结构、显微硬度和摩擦磨损性能进行了测试与分析,并与Ni-P镀层和基材进行了对比。结果表明,Ni-P/nano-Al_2O_3复合镀层的晶粒细小,结构更加致密,显微硬度平均值可达到436.4 HV,高于Ni-P镀层的357.3 HV和基材的190HV;与Ni-P镀层相比,Ni-P/nano-Al_2O_3复合镀层能更有效地改善基材的摩擦磨损性能。NanoAl_2O_3颗粒复合量对Ni-P/nano-Al_2O_3复合镀层的显微硬度和摩擦磨损质量损失率有一定影响,增加颗粒复合量可以提高复合镀层的显微硬度,改善其摩擦磨损性能。     

工艺参数对塑料板搅拌摩擦焊的影响

采用搅拌摩擦焊对聚丙烯塑料板材进行焊接试验。结果表明:搅拌头旋转速度、焊接速度及其对塑料板上表面的压力等因素都会影响焊接效果。但是,只要各参数选取恰当,焊接效果就会很好。     

温度及表面金属化对铝基复合材料与可伐合金真空钎焊的影响

采用Al63-Cu22-Ti5-Si10钎料,研究了55%SiCp/6063Al复合材料和可伐合金之间的真空钎焊工艺,分析了钎焊温度和复合材料表面镀层材料对接头抗剪强度和显微硬度的影响规律,并对接头的显微组织进行了研究。结果表明钎焊温度和复合材料表面镀层对接头的力学性能影响很大,在同样的焊接参数下,复合材料表面镀铜的试样,其抗剪强度要高于无镀层和镀镍的试样,镀铜试样的最高抗剪强度为92.8 MPa。当钎焊温度从560℃增加到580℃时,接头的抗剪强度逐渐降低再上升,经过不同表面处理的试样均在钎焊温度为560℃时达到最大抗剪强度。钎焊温度相同时,镀铜试样的显微硬度均最高,而镀镍试样的显微硬度最低。焊缝组织致密,没有出现孔洞和未润湿等钎焊缺陷,钎焊完成后,接头中镀层被钎料取代而消失。在保温时间为30 min、真空度6.5×10-3 Pa条件下,采用Al63-Cu22-Ti5-Si10钎料,55%SiCp/6063Al复合材料与可伐合金真空钎焊合理钎焊温度为560℃,合理镀层为镀铜。     

Material deformation and removal mechanism of SiCp/Al composites in ultrasonic vibration assisted scratch test

The material removal process of SiCp/Al composites is a result of synergetic deformation and interaction among Al matrix, SiC particles and interface. The non-homogeneity of microscopic mechanical properties due to the inherent polyphase heterogeneity of SiCp/Al composites will directly affect the removal mechanism and surface integrity in the machining process. This paper aims to gain further insight of the material deformation and removal mechanism of SiCp/Al composites in ultrasonic vibration assisted machining process. The elastic modulus and hardness of SiCp/Al composites were determined through the indentation test by loading on Al matrix and SiC particles, respectively. Due to the interaction effects of the three phases during the deformation process, when the indenter is on a single phase, the influence of the other phases cannot be neglected and is reflected in the P-h curves. Scratch force, friction coefficient and material removal behavior were investigated in traditional scratch (TS) and ultrasonic vibration assisted scratch (US) tests. In most cases, with the assistance of ultrasonic vibration, scratch force and friction coefficient in US process are smaller than those in TS process, and the reduction of them is modeled and analyzed. The material removal behavior of SiCp/Al composites is similar to metal at the macroscale, and a high material removal rate is achieved in US process. SiC particles tend to maintain the structural integrity rather than be fractured or pulled out in US process. The scratched surface in TS process is damaged to a greater degree than that subjected to US process.     

Investigations on Mechanical and Metallurgical Properties of Friction Welding of AlB<Subscript>2</Subscript> Reinforced Aluminum Matrix Composites

Friction stir welding (FSW) of AlB₂ reinforced aluminum matrix composites was conducted by varying two process parameters namely rotational speed of the tool and travelling speed. Six welds were made on the metals to determine the optimum level of process parameters for welding aluminum matrix composites. Microstructures evaluation conducted by optical microscopy (OM) and scanning electron microscopy shows the boron particle agglomerations at the interface of joints form larger grain structures in the stir zone (SZ). Mechanical properties were investigated using a tensile strength test and microhardness measurements. The joints made with rotational speed of 1000 rpm and travelling speed of 10 mm/min exhibit the highest strength of 152.7 MPa in the weld zone. The friction coefficient, wear behavior and scratch morphology of the friction stir welded AMCs were studied. The hardness and wear properties improved in the base metal region in comparison to the welded region.     

Microstructures and mechanical properties of thin 304 stainless steel sheets by friction stir welding

Friction stir welding (FSW) was performed on 304 stainless steel sheets. The welding speed was varied from 30 to 70 mm/min. Because the FSW of thin plates is sensitive to heat input. The surface of the welds is smooth and without any macroscopic cracks and cavities only when the rotation speed is 50 mm/min. The stir zone had equiaxed grains with austentic structure due to dynamic recrystallization. There was not any evidence for the presence of sigma phases being found in this study. Meanwhile, there was a weak region in the advancing side because of the flow of plastic metals. However, compared with the base material, mechanical properties of the joint are maintained in a comparatively high level.     

A Study on the Effect of Incorporation of SiC Particles during Friction Stir Welding of Al 5059 Alloy

Silicon - Friction stir welding (FSW) was performed in the current research on Al 5059 alloy. Nano-sized SiC (n-SiC) particles were incorporated during FSW for improving mechanical characteristics...     

Effect of interfacial-active elements addition on the incorporation of micron-sized SiC particles in molten pure aluminum

Ceramic particles generally have poor wettability by liquid metal, leading to a major drawback in fabrication of cast metal matrix composites (MMCs). In this work,  the effect of 1 wt. % of Ca, Mg, Si, Ti, Zn and Zr interfacial-active alloying elements was studied on the incorporation of micron-sized SiC particles into the molten pure aluminum using the vortex casting method at 680 °C. The results indicated that Ti, Zr, Zn and Si were not positively effective in improving particulate incorporation, while Ca and especially Mg were very efficient at increasing the incorporation of ceramic particles into the molten Al. Also, it was revealed that Al₃Ti, and Al₃Zr intermetallic phases were formed for samples containing Ti and Zr, making hybrid MMCs with a higher amount of hardness. Finally, it was found that a reaction layer between Al and SiC particles was formed at the Al/SiC interface for all of the samples, expect for the ones containing Si and Ti, indicating that for most of the samples at 680 °C an exothermic reaction took place between the Al and SiC particles.     

Studies on Fractures of Friction Stir Welded Al Matrix SiC-B<Subscript>4</Subscript>C Reinforced Metal Composites

Studies pertaining to joining of Al alloy metal matrix composites reinforced with B₄C and SiC by solid state friction stir welding (FSW) are presented in this paper. FSW tool dimensions are designed and fabricated to suit the weld sample dimensions and subsequently, the implications of the tool pin profile on the weldability is investigated. Through experimental recordings, the heat generated during the friction stir joining process of composites is estimated by developing relative equations. Maintaining the tool traverse speed constant, the rate of rotation and its effects on the tensile strength at the joints are investigated which reveals reduced ductility. The study emphasizes that when the speed is maintained between 100–400 mm/min, the tensile strength is at its optimal maximum while speeds higher or lower than the optimal range indicate detrimental effects on the tensile strength. This is followed by fracture studies on samples welding with varying traverse speed and rate of welding. Traverse speed appears to govern the fracture modes while brittle fracture is predominantly noticed indicating the importance of feeding optimal heat input during joining.     

Study on Mechanical and Tribological Characterization of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/SiCp Reinforced Aluminum Metal Matrix Composite

In this investigation, an attempt has been made to hardness and wear rate of Al7075 hybrid metal matrix composite reinforced with the hard ceramics like alumina (2, 4, and 6 wt.% of Al2O3) and silicon carbide (3, 6, and 9 wt.% of SiC) is fabricated by using stir casting method. The samples were aging at temperature of 140 ^°C, 160 ^°C and 180 ^°C and monitored by hardness test. Taguchi’s L27 Orthogonal array was used for optimizing the process parameters. The obtained results indicated that hardness increased with increasing reinforcement. A wear test was performed using pin-on disk apparatus at room temperature for constant load of 30N, at a fixed sliding speed of 1.66 m/s and wear resistance increased as the weight percentage of reinforcement increased. Scanning electron microscope (SEM) studies were carried out to evaluate the worn surface. From the analysis of variance (ANOVA), Al₂O₃ is the significant factor that affects the hardness and wear loss of hybrid composites followed by SiCp and heat treatment. Confirmatory test was performed for the optimized parameters and these results were within the acceptable range when compared with the experimental results.     

Finite element analysis and experimental investigation of ultrasonic testing of internal defects in SiCp/Al composites

Revealing the interactions of sound waves with both SiC particles and internal defects is crucial for facilitating the detectability of internal defect features in SiCp/Al by using ultrasonic testing (UT). In the present work, we demonstrate the feasibility of UT of internal flat-bottom holes with diameters ranging from 0.2 mm to 2 mm in SiCp/Al composites through the combination of finite element (FE) simulations and experiments. Specially, a 2D FE model of UT of SiCp/Al with consistent geometrical features of SiC particles with experimental one is established, the accuracy of which is validated by theoretical and experimental characterizations of P-wave velocity and ultrasonic attenuation coefficient of SiCp/Al. Subsequently, the propagation behavior of sound waves in the SiCp/Al specimen with pre-existing defects under UT, in particular the impact of defect boundary on the scattering behavior of sound waves, is revealed in detail by FE simulations and also validated by corresponding experiments. Furthermore, the UT limit of detectable size of the internal defects is revealed jointly by FE simulations and experiments, based on which a correlation map between defect size and echo signal amplitude is established. Current study provides theoretical and practical guidance for the UT of internal defects in SiCp/Al composites.     

SiCp/Al复合材料的自发熔渗机理

以Mg为助渗剂,采用液态铝自发熔渗经氧化处理的SiC粉体压坯的方法,制备出高增强体含量的SiCp/Al复合材料.通过考察铝液在SiC粉体压坯中的渗入高度与温度、时间的关系来研究铝液的熔渗机理,并对SiCp/Al复合材料进行X射线衍射、能量散射谱和金相分析.结果表明:在熔渗前沿发生的液-固界面化学反应促进两相润湿,毛细管力导致铝液自发渗入到SiC多孔陶瓷中;熔渗高度与时间呈抛物线关系.熔渗激活能为166 kJ/mol,这表明渗透过程受界面反应控制.经氧化处理的SiC粉体均匀地分布在金属基体中,其轮廓清晰.在SiCp/Al复合材料中未发现Al4C3的存在.